The first Homelite chainsaw?

[John in MA]

No, no humor in this one. Is this the first Homelite chainsaw? I've never seen anything this old from them.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2311195421&category=20538

 

[eyolf]

Is that really a Homelite, or did the seller advertize it that way to get more clicks?

They did say DESA int'l, but I think DESA is a newer name for a conglomerate that has swallowed up a lot of older companies...one of which was Emerson Electric, formerly allioed with Bearde-Poulan...making it the first "wild thing"

 

[kam]

Desa made Remington chainsaws (Mighty-Mite),
in the early 80's. "Worst chainsaw ever made."

 

[Greg Carberry]

Heres the ECS:

http://www.acresinternet.com/cscc.n...21a9a51052e687d488256b86001d0f57?OpenDocument

Though the one in the auction looks a little difftrent than those. Those are some crazy saws, 3 phase and with their own generators!

 

[Mike Acres]

I don't think this guy has his listing correct. Homelite is Homelite which we know was a divsion of Textron and was then sold to John Deere.
DESA is REMINGTON and the two companies did not have any working relationship that I know of. The saw in the picture is quite small and does not resemble anything Homelite built that I am familiar with.

 

[treeslayer]

Better ask more about the power source before you buy this one,
230volts? 3 phase? must be AC. standard 3 phase is 208vac, it would still work, but what the heck, its only $80 bucks now.

 

[John in MA]

It depends on the 3ph configuration. Lots of setups use 230VAC.

The 180 cycles is the interesting part. I would assume it's that to reduce the mass of the truck generator required to run it.

 

[dbabcock]

A line frequency of 180 Hz. and the fact that the motor is 3 phase both work in favor of a reduction of size and weight for the saw and generator. Running the saw on 208 won't hurt it, but trying to run a 180 Hz unit at 60 Hz. will fry it for sure! The requirement of a 5 KVA genset says that the crank HP was probably well under 5.

 

[treeslayer]

180 cycles? wow. A 60 cycle feed would burn it up for sure. you think thats to reduce windings?
5000 watts divided by 746 =6.7 power factor of 3.57 for 3 phase= almost 8hp? potentially.

3 phase is 208 delta config from a wye transformer in commercial service, at least around here.
230 is usually single phase 2 pole. but then I'm just a youngster,
and it is a big world out there....

d**n, this makes my head hurt.

 

[glens]

Doug, it appears via the acres link that the 5KVA unit was for feeding two heads and the 2.5KVA for a single, so don't forget to factor <i>that</i> into the W -> HP conversion.

It also appears as though there's (at the least, but most likely) a single reduction from the motor to the sprocket.&nbsp; The line frequency is probably so high merely to achieve a suitable motor speed.&nbsp; Would running it at 60Hz damage it or just cause it to produce 1/3 the power and speed?

Glen

 

[dbabcock]

Why would power factor get into the equation? 5000 Watts is 6.7 HP into the saw, period.

Glen,
I didn't realize that the 5 KVA genset powered two heads. That's good then. Let's see: a 150 lb. generator powering two 20+ pound saws equals 2 wickedly detuned 3120's and half a dozen cinder blocks. Motor speed is derived from line frequency, but it's the number of poles combined with the line frequency that determine the motor's synchronous RPM. Same area under the curve whether it's 60 or 180 Hz, so power input is the same. 180 Hz. makes the motor's magnetic field components smaller because of the higher frequency. Running a lower frequency into such a motor merely reduces efficiency because field coupling will be lower. This reduction in efficiency produces heat. Heat is bad.

 

[Rotax Robert]

D.B. is correct and beat me at the keyboard as that was what I was typing ...Verbatim.

 

[glens]

Almost two years ago there was an auction containing "(3) Homelite 5000 watt high-cycle generators (1 for parts)" (http://www.southfloridaauction.com/042801/, with image).&nbsp; Maybe they could be tracked down?

I'm having a little trouble grokking the "badness" of running an AC motor at an alternate frequency.&nbsp; Hey, I admit I'm not up on all the latest and/or minuti&aelig; (Hi Fish and Tony!), but variable speed control is provided by inverters producing variable frequency power these days, isn't it?&nbsp; Aren't they capable of "soft starts" and speed ranges from full to approaching nothing?&nbsp; Are they manipulating voltage levels in specific ways as well?

I've done a little bit of googling and found, among other sources, http://e-www.motorola.com/webapp/sps/site/overview.jsp?nodeId=03nQXG3MYxCKS2JjTF#acmotors, where at the midpoint of the first paragraph my basic understanding seems to be confirmed, at least in part.

I'm not suggesting that full rated torque will be developed, and if it's a third of what would normally be the equivalent of an MS260 it's a moot point (if it isn't long before then).

I guess what I'm having trouble seeing is the power draw of the motor being the same at both full- and at 1/3-frequency/rotation.&nbsp; I'd think that the power draw, although certainly somewhat greater than a factor of .33, would be sufficiently lower that destructive levels of heat would not be produced.

Can you point me to a ready source of educational information, Doug (or Robert :<i></i>)?

Glen

 

[dbabcock]

Variable speed controls change motor speed by varying duty cycle, not frequency. As to a good source of info on this subject, I cannot tell a lie...Rotax Robert taught me all I know.

 

[Gypo Logger]

Glen,
I didn't realize that the 5 KVA genset powered two heads. That's good then. Let's see: a 150 lb. generator powering two 20+ pound saws equals 2 wickedly detuned 3120's and half a dozen cinder blocks. Motor speed is derived from line frequency, but it's the number of poles combined with the line frequency that determine the motor's synchronous RPM. Same area under the curve whether it's 60 or 180 Hz, so power input is the same. 180 Hz. makes the motor's magnetic field components smaller because of the higher frequency. Running a lower frequency into such a motor merely reduces efficiency because field coupling will be lower. This reduction in efficiency produces heat. Heat is bad.
The field coupling is dependent upon the gauge of the wire in the primary winding, thus we have an overloaded circuit without the required resistance to cause the bi-polar confluence of the axiometrical frequency, thus reducing rpm.
John

 

[mbopp]

I've seen speed controls that use variable duty cycle, also variable frequency. I worked in an industrial instrumentation flow lab, and they had some ABB pumps that used variable frequency for speed control in the calibration lines.

I know increasing the frequency cuts the amount of iron needed in a transformer, as I recall aircraft use 400 Hz AC for that reason.

Hey Doug, perhaps upping the frequency also cuts the weight and increases the speed in an induction motor?

 

[glens]

I inferred the weight/speed bit in my earlier (first?) post in this thread.

I just devoted a few more minutes to some research and it appears as though the voltage does in fact need to be varied as well as the frequency.&nbsp; I acknowledge that running the saw at the same (or very near) voltage but 1/3 the frequency would be highly detrimental in terms of usable power, and probably fatal to the motor.&nbsp; Might as well rock the chain out real good first and make a spectacular showing of it (don't forget to wear the asbestos gloves).

Here are a few pertinent links:

http://www.lmphotonics.com/vsd/vsd_01.htm#variablef
http://www.lmphotonics.com/faq.htm#ospeed_vfd
http://www.lmphotonics.com/faq.htm#60_50

Glen

 

[dbabcock]

I just had a quick conference call with my two high tech mentors, Rotax and Gypo. What they told me boils down to this (which they said was sufficient for this chainsaw forum because it's not an electric motor forum):

Concerning inefficiency of running 180 Hz. motor at 60 Hz. frequency: Leakage inductance of the motor windings will cause bigtime losses at lower frequencies. The motor can drive the same load, but the heat losses will be tremendous, so don't run it for long like this.

Concerning input voltage relation to speed: Enough input voltage must be present to at least cancel the back EMF of the motor, which is of course, load related. Under light loading, input voltage may be reduced. As long as input voltage is enough to compensate back EMF, then the motor will essentially run sychronously, which means proportional to the line frequency and number of poles.

As far as Gypo's observation relating to "bi-polar confluence of the axiometrical frequency", it's way over my head and since he's the Yoda of the high tech world, why wouldn't it be?

 

[glens]

Yes, why wouldn't he, and why wouldn't it?&nbsp; Ha, ha, ha.

Is this thing beat deep enough into the ground yet?&nbsp; If it wasn't before maybe it will be now...

Glen

 

[dbabcock]

It's good to see that you're one of the first to finally see it our way, Glen; and why wouldn't you. Hmhmhm. More lessons will follow soon on what it takes to be hip. Just keep in mind that what's hip today might become passe.